ExpandAllRecords function for Power Query or Power BI - expands all record-type columns recursively

ExpandAllRecords.M

// Based on Chris Webb's blog post - http://blog.crossjoin.co.uk/2014/05/21/expanding-all-columns-in-a-table-in-power-query/

let

    // Define function taking two parameters - a table and an optional column number 
    Source = (IncomingTableToExpand as table, optional ColumnNumber as number) =>

    let
        // Buffer the table for performance
        TableToExpand = Table.Buffer(IncomingTableToExpand),

        // If the column number is missing, make it 0
        ActualColumnNumber = if (ColumnNumber=null) then 0 else ColumnNumber,

        // Find the column name relating to the column number
        ColumnName = Table.ColumnNames(TableToExpand){ActualColumnNumber},
        
        // Get a list containing all of the values in the column
        ColumnContents = Table.Column(TableToExpand, ColumnName),

        // Iterate over each value in the column and then
        // If the value is of type table get a list of all of the columns in the table
        // Then get a distinct list of all of these column names
        ColumnsToExpand = List.Distinct(
            List.Combine(
                List.Transform(
                    ColumnContents, 
                    each if _ is record 
                        then Record.FieldNames(_) 
                        else {}
                )
            )
        ),

        // Append the original column name to the front of each of these column names
        NewColumnNames = List.Transform(ColumnsToExpand, each ColumnName & "." & _),

        // Is there anything to expand in this column?
        CanExpandCurrentColumn = List.Count(ColumnsToExpand) > 0,

        // If this column can be expanded, then expand it
        ExpandedTable = if CanExpandCurrentColumn 
            then Table.ExpandRecordColumn(TableToExpand, ColumnName, ColumnsToExpand, NewColumnNames) 
            else TableToExpand,

        // If the column has been expanded then keep the column number the same, otherwise add one to it
        NextColumnNumber = if CanExpandCurrentColumn then ActualColumnNumber else ActualColumnNumber + 1,

        // If the column number is now greater than the number of columns in the table
        // Then return the table as it is
        // Else call the ExpandAll function recursively with the expanded table
        OutputTable = if NextColumnNumber>(Table.ColumnCount(ExpandedTable)-1) 
            then ExpandedTable 
            else ExpandAllRecords(ExpandedTable, NextColumnNumber)

    in
        OutputTable
in
    Source